Pump apparatus

ABSTRACT

In a variable displacement vane pump, a cam profile of a cam ring includes a deviation region deviating from a perfect-circle cam profile outwardly in a radial direction regarding a rotational axis of a driving shaft in an intake region.

TECHNICAL FIELD

The present invention relates to a pump apparatus.

BACKGROUND ART

PTL 1 discloses a variable displacement vane pump in which vanes are contained in slits in a projectable and retractable manner, and change the volumes of pump chambers Ruined among the inner peripheral edge of a cam ring, the outer peripheral edge of a rotor, and the vanes. The vanes are biased in directions for projecting from the slits by the pressures of hydraulic oil introduced into back-pressure chambers of the rotor.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Public Disclosure No. 2013-194677

SUMMARY OF INVENTION Technical Problem

However, according to the above-described patent literature, PTL 1, the distal ends of the vanes are pressed against the inner peripheral edge of the cam ring and this promotes local wear of the distal ends of the vanes in an intake region where the pressures in the pump chambers fall below the pressures in the back-pressure chambers. This local wear may lead to a shortage of an oil film due to a reduction in the viscosity of hydraulic oil interposed between the vanes and the cam ring, thereby resulting in galling and seizure accompanying a contact between the metal materials.

Solution to Problem

One of objects of the present invention is to provide a pump apparatus capable of reducing local wear of a distal end of a vane.

In a pump according to one aspect of the present invention, a cam profile of a cam ring includes a deviation region deviating from a perfect-circle cam profile outwardly or inwardly in a radial direction regarding a rotational axis of a driving shaft in an intake region.

Advantageous Effects of Invention

According to this configuration, in the intake region, the pump can cause a change in a sliding range of the distal end of the vane in contact with an inner peripheral edge of the cam ring according to a phase, thereby reducing the local wear of the distal end of the vane. As a result, the pump can reduce galling and seizure between the distal end of the vane and the inner peripheral edge of the cam ring.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an axial cross-sectional view illustrating a variable displacement vane pump 1 according to a first embodiment.

FIG. 2 is a cross-sectional view taken along a line indicated by arrows S2-S2 illustrated in FIG. 1.

FIG. 3 is a back view of a cam ring 8 according to the first embodiment.

FIG. 4 illustrates a cam profile radius change rate with respect to a cam profile angle according to the first embodiment.

FIG. 5 illustrates the cam profile radius change rate with respect to the cam profile angle when the cam ring is deformed according to the first embodiment.

FIG. 6 illustrates the shape of the distal end of a vane 16 according to the first embodiment.

FIG. 7 illustrates a contact range between a vane distal end curved surface portion 16 a and an inner peripheral edge 8 a of the cam ring 8 according to the first embodiment.

FIG. 8 illustrates a vane contact position with respect to a pump rotational angle according to the first embodiment.

FIG. 9 illustrates the cam profile radius change rate with respect to the cam profile angle when the cam profile radially inwardly deviates from a perfect-circle cam profile.

FIG. 10 illustrates an effect of expanding the vane contact range according to the first embodiment.

FIG. 11 illustrates the relationship between a rotational axis O of a driving shaft 6 and a center P of the inner peripheral edge 8 a of the camp ring 8 in the variable displacement vane pump (a pump apparatus) 1 according to a second embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is an axial cross-sectional view illustrating a variable displacement vane pump (a pump apparatus) 1 according to a first embodiment. FIG. 2 is a cross-sectional view taken along a line indicated by arrows S2-S2 illustrated in FIG. 1.

The variable displacement vane pump 1 includes a pump housing 4 and a pump element 5. The variable displacement vane pump 1 exerts a pump function by rotationally driving the pump element 5 by a driving shaft 6. The pump housing 4 is formed by bringing a front housing 2 and a rear housing 3 into abutment with each other. The pump housing 4 contains the pump element 5 in a pump element containing space 4 a. The pump element 5 includes a rotor 7 and a cam ring 8. The rotor 7 rotates integrally with the driving shaft 6. The cam ring 8 is positioned on the outer peripheral side of the rotor 7, and is formed generally annularly from a metallic material. The cam ring 8 is swingable in a direction for changing an eccentricity amount with respect to the rotor 7. The pump housing 4 includes an adapter ring 9 and a pressure plate 10. The adapter ring 9 is positioned on the outer peripheral side of the cam ring 8, and has a generally annular shape. The adapter ring 9 is fixed to the outer peripheral cylindrical surface of the pump element containing space 4 a. The pressure plate 10 is positioned on an inner bottom surface 2 a of the front housing 2 in the pump element containing space 4 a, and has a generally disk-like shape.

The adapter ring 9 and the pressure plate 10 are restricted from rotating relative to the pump housing 4 by a positioning pin 11. A plate member 12 is set up on a clockwise side of the positioning pin 11 in FIG. 2 (a first fluid pressure chamber 14 a side, which will be described below). The plate member 12 has a function as a supporting point for the swinging movement of the cam ring 8, and a seal function of sealing between the cam ring 8 and the adapter ring 9. A seal member 13 is disposed at a position of the inner peripheral edge of the adapter ring 9 radially opposite from the plate member 12. The seal member 13 seals between the adapter ring 9 and the cam ring 8. The seal member 13 and the plate member 12 form a pair of fluid pressure chambers 14 a and 14 b between the cam ring 8 and the adapter ring 9. More specifically, the first fluid pressure chamber 14 a and the second fluid pressure chamber 14 b are formed on one radial side and the other radial side of the cam ring 8, respectively. The eccentricity amount of a center (a central axis) P of the inner peripheral edge of the cam ring 8 with respect to a rotational axis O of the driving shaft 6 increases and reduces according to the swinging movement of the cam ring 8 clue to a pressure difference between these fluid pressure chambers 14 a and 14 b. The cam ring 8 is constantly biased by a return spring 15 in a direction for maximizing the eccentricity amount with respect to the rotor 7 (a maximum eccentricity side).

The rotor 7 includes a plurality of slits 7 a cutout along the radial direction on the outer peripheral portion thereof. These slits 7 a are arranged at equal pitches in the circumferential direction regarding the rotational axis O of the driving shaft 6. Vanes 16 are contained in the slits 7 a in a projectable and retractable manner in the radial direction of the rotor 7, respectively. Each of the vanes 16 is formed into a generally flat plate-like shape from a metallic material. Each of the vanes 16 partitions an annular space between the cam ring 8 and the rotor 7 circumferentially, by which a plurality of pump chambers 17 is formed. Rotationally driving the rotor 7 in the counterclockwise direction in FIG. 2 by the driving shaft 6 causes each of the pump chambers 17 to engage in a circling movement while increasing and reducing the volume thereof, thereby achieving the pump function. Each of the vanes 16 is pressed against the inner peripheral edge of the cam ring 8 by the pressure of hydraulic oil introduced into a back-pressure chamber 7 b formed on the inner peripheral side of each of the slits 7 a.

A first intake port 18 is formed in a portion corresponding to an intake region in which the volume of each of the pump chambers 17 gradually increases according to the rotation of the rotor 7 on an inner surface 3 a of the rear housing 3 that faces the pump element containing space 4 a. The first intake port 18 has a generally crescent-like shape extending along the circumferential direction as viewed in the front view. The first intake port 18 is in communication with an intake passage 19 a formed in the rear housing 3. Due to this configuration, the hydraulic oil introduced into the intake passage 19 a via an intake pipe 20 connected to a not-illustrated reservoir tank is sucked into each of the pump chambers 17 with the aid of a pump intake function in the above-described intake region.

A second intake port 21 is formed at a position opposite from the first intake port 18 on the surface of the pressure plate 10 that faces the rotor 7. The second intake port 21 is shaped approximately identically to this first intake port 18. An intake region corresponds to the range from a start end 21 a to a termination end 21 b of the second intake port 21 in the circumferential direction. The same also applies to the first intake port 18. The second intake port 21 is in communication with a return flow passage 22 formed in the front housing 2. The return flow passage 22 is in communication with a recessed portion of the front housing 2 that contains a seal member sealing between the front housing 2 and the driving shaft 6. Extra oil of the above-described seal member is supplied into each of the pump chambers 17 due to the intake function in the above-described intake region, thereby being prevented from leaking outward.

A first discharge port 23 is formed in a portion corresponding to a discharge region in which the volume of each of the pump chambers 17 gradually reduces according to the rotation of the rotor 7 on the surface of the pressure plate 10 that faces the rotor 7. The first discharge port 23 has a generally crescent-like shape extending along the circumferential direction as viewed in the front view. A discharge region corresponds to the range from a start end 23 a to a termination end 23 b of the first intake port 23 in the circumferential direction. The same also applies to a second discharge port 25, which will be described below. The first discharge port 23 is in communication with a discharge passage 19 b via a pressure chamber 24 formed in a recessed manner on the inner bottom surface 2 a of the front housing 2 that faces the pressure plate 10. Due to this configuration, the hydraulic oil discharged from each of the pump chambers 17 with the aid of a pump discharge function in the above-described discharge region is discharged to outside the pump housing 4 via the pressure chamber 24 and the discharge passage 19 b, and is transmitted to a hydraulic power cylinder of a not-illustrated power steering apparatus. The pressure plate 10 is pressed toward the rotor 7 side by the pressure in the pressure chamber 24.

The second discharge port 25 is formed at a position on the inner surface 3 a of the rear housing 3 opposite from the first discharge port 23. The second discharge port 25 is shaped approximately identically to this first discharge port 23. These intake ports 18 and 21 and these discharge ports 23 and 25 are each disposed axially symmetrically with respect to each of the pump chambers 17, and this layout allows pressure balance to be maintained on both axial sides of each of the above-described pump chambers 17.

A control valve 26 is provided in a direction perpendicular to the driving shaft 6 (the horizontal direction in FIG. 2) inside the upper end side of the front housing 2. The control valve 26 controls a pump discharge pressure. The control valve 26 is formed in the front housing 2 from the left side toward the right side in FIG. 2. The control valve 26 includes a valve hole 28, a spool 29, and a control valve spring 30. An opening portion of the valve hole 28 on the left side in FIG. 2 is closed by a plug 27. The spool 29 is axially slidably contained in the valve hole 28. The spool 29 is a spool valve body having a generally bottomed cylindrical shape. The control valve spring 30 biases the spool 29 toward the plug 27 side. The control valve spring 30 is a cylindrical compression coil spring.

A high-pressure chamber 28 a, an intermediate-pressure chamber 28 b, and a low-pressure chamber 28 c are defined by the spool 29 in the valve hole 28. A hydraulic pressure on the upstream side of a not-illustrated metering orifice formed in the discharge passage 19 b, i.e., a hydraulic pressure in the pressure chamber 24 is introduced into the high-pressure chamber 28 a. The intermediate-pressure chamber 28 b contains the control valve spring 30, and a hydraulic pressure on the downstream side of the above-described metering orifice is introduced into the intermediate-pressure chamber 28 b. The low-pressure chamber 28 c is formed on the outer peripheral side of the spool 29, and a pump intake pressure is introduced from the intake passage 19 a into the low-pressure chamber 31.

The spool 29 is axially moved according to a pressure difference between the intermediate-pressure chamber 28 b and the high-pressure chamber 28 a. More specifically, when the pressure difference between the intermediate-pressure chamber 28 b and the high-pressure chamber 28 a is relatively small and the spool 29 is in a state in abutment with the plug 27, a communication passage 32, which establishes communication between the first fluid pressure chamber 14 a and the valve hole 28, is opened to the low-pressure chamber 28 c, and the relatively low hydraulic pressure in the low-pressure chamber 28 c is introduced into the first fluid pressure chamber 14 a. On the other hand, when the pressure difference between the intermediate-pressure chamber 28 b and the high-pressure chamber 28 a increases and the spool 29 is axially moved against the biasing force of the control valve spring 30, the communication between the low-pressure chamber 28 c and the first fluid pressure chamber 14 a is gradually blocked and the high-pressure chamber 28 a is brought into communication with the first fluid pressure chamber 14 a via the communication passage 32. As a result, the relatively high hydraulic pressure in the high-pressure chamber 28 a is introduced into the first fluid pressure chamber 14 a. In other words, the hydraulic pressure in the low-pressure chamber 28 c or the high-pressure chamber 28 a is selectively introduced into the first fluid pressure chamber 14 a.

The pump intake pressure is constantly introduced into the second fluid pressure chamber 14 b. When the hydraulic pressure in the low-pressure chamber 28 c is introduced into the first fluid pressure chamber 14 a, the cam ring 8 is located at a position where the eccentricity amount with respect to the rotor 7 is maximized (a position on the left side in FIG. 2) due to the biasing force of the return spring 15. At this time, the pump discharge amount is maximized. On the other hand, when the hydraulic pressure in the high-pressure chamber 28 a is introduced into the first fluid pressure chamber 14 a, the cam ring 8 swings so as to reduce the volume of the second fluid pressure chamber 14 b against the biasing force of the return spring 15 due to the pressure in this first fluid pressure chamber 14 a, thereby reducing the eccentricity amount between this cam ring 8 and the rotor 7. The pump discharge amount reduces according to the reduction in the eccentricity amount.

A relief valve 33 is formed inside the spool 29. The relief valve 33 maintains a valve-closed state when the pressure in the intermediate-pressure chamber 28 b is lower than a predetermined pressure. When the pressure in the intermediate-pressure chamber 28 b reaches or exceeds the predetermined pressure, i.e., the pressure on the power steering apparatus side (the load side) reaches or exceeds the predetermined pressure, the relief valve 33 is brought into a valve-opened state to start a relief operation, thereby causing the hydraulic oil to return to the intake passage 19 a via the low-pressure chamber 28 c and a low-pressure passage 31. In other words, the relief valve 33 opens and closes an oil passage between the discharge passage 19 b and the intake passage 19 a.

FIG. 3 is a back view of the cam ring 8 according to the first embodiment. FIG. 3 illustrates the cam ring 8 at the time of the maximum eccentricity (in a state that the eccentricity amount of the center (the central axis) P of the inner peripheral edge of the cam ring 8 with respect to the rotational axis O is maximized).

In FIG. 3, a first axis L1 is defined to refer to an axis extending perpendicularly to the rotational axis O and passing through a point p1 that divides in half a section between the termination end 23 b of the first discharge port 23 and the start end 21 a of the second intake port 21 in the circumferential direction around the rotational axis O. A second axis L2 is defined to refer to an axis extending perpendicularly to the first axis L1 and passing through a point p4 that divides in half a section between a pair of intersection points p2 and p3 at which the cam profile and the first axis L1 intersect with each other. The intersection point p4 between the first axis L1 and the second axis 12 is defined to be a cam profile central point. A third axis L3 is defined to refer to an axis passing through the cam profile central point p4 and the termination end 21 b of the second intake port 21. A perfect-circle cam profile radius r0 is defined to refer to the length between a point p5 at which the third axis L3 and the cam profile intersect with each other and the cam profile central point p4. A perfect-circle cam profile is defined to refer to a circular arc centered at the cam profile central point p4 and having the perfect-circle cam profile radius r0. The cam profile according to the first embodiment includes a deviation region deviating from the perfect-circle cam profile outwardly in the radial direction of the rotational axis O throughout the entire intake region at the time of the maximum eccentricity. In other words, the cam profile of the cam ring 8 according to the first embodiment is set in such a manner that the cam profile radius r at the time of the maximum eccentricity exceeds the perfect-circle cam profile radius r0 throughout the entire intake region. A region corresponding to r longer than r0 in the cam profile is the deviation region.

In FIG. 3, a cam profile radius change rate [dr/dθ] is defined to refer to the change rate of the cam profile radius r in the rotational direction of the driving shaft 6 (the counterclockwise direction). Further, a cam profile defining angle 0 [deg] is set to a point on the intake region side that is one of a pair of points on the inner peripheral edge 8 a of the cam ring 8, i.e., the cam profile that intersects with a straight line passing through the center P and the start end 21 a of the second intake port 21 when the cam ring 8 is disposed in such a manner that the center P of the cam ring 8 coincides with the rotational axis O. Then, a cam profile defining angle (a cam profile angle) θ is defined in such a manner that the angle increases toward the rotational direction of the driving shaft 6 along the inner peripheral edge 8 a at each point on the inner peripheral edge 8 a of the cam ring 8, and reaches 360 [deg] at the completion of one round along the inner peripheral edge. FIG. 4 illustrates the cam profile radius change rate with respect to the cam profile angle. At the time of the maximum eccentricity, the cam profile radius change rate in the intake region has a positive sign and increases according to an increase in the cam profile angle θ and then starts to reduce after that. The cam profile radius change rate in the discharge region has a negative sign and reduces according to an increase in the cam profile angle θ and then starts to increase after that. In other words, the cam profile radius r is longer than the perfect-circle cam profile radius r0 throughout the entire intake region and is shorter than the perfect-circle cam profile radius r0 throughout the entire discharge region. In sum, the cam profile of the cam ring 8 in the intake region bulges radially outwardly with respect to the perfect circle.

On the other hand, the cam profile radius change rate in the intake region at the time of the minimum eccentricity is lower than that at the time of the maximum eccentricity, and therefore the cam profile radius change rate has a negative sign in a region accounting for a little more than one-third of the intake region but keeps a positive sign in a region accounting for a little less than two-thirds. In other words, the cam profile of the cam ring 8 includes the deviation region even at the time of the minimum eccentricity.

FIG. 5 illustrates the cam profile radius change rate with respect to the cam profile angle when the cam ring is deformed according to the first embodiment. When the variable displacement vane pump 1 is in operation (when the driving shaft 6 rotates), the cam ring 8 is deformed in a direction for reducing the cam profile radius change rate in the intake region and increasing the cam profile radius change rate in the discharge region due to the discharge pressure (the pump inner pressure) applied to the discharge region. Now, a cam profile radius r1 in a first state is defined to refer to the cam profile radius of the cam profile (the cam profile in the first state) when the variable displacement vane pump 1 is out of operation (when the driving shaft 6 is stopped). Further, a cam profile radius r2 in a second state is defined to refer to the cam profile radius of the cam profile (the cam profile in the second state) when the variable displacement vane pump 1 is in operation (when the driving shaft 6 rotates). Then, a first cam profile deviation amount Δr1 is defined to refer to the maximum value of the absolute value of the difference when comparing the cam profile radius r1 in the first state and the cam profile radius r2 in the second state corresponding to the same cam profile angle θ. Further, a second cam profile deviation amount Δr2 is defined to refer to the maximum value of the absolute value of the difference when comparing the cam profile radius r1 in the first state and the perfect-circle cam profile radius r0 corresponding to the same cam profile angle θ. The cam ring 8 according to the first embodiment has such a shape that the cam profile in the first state satisfies Δ1<Δr2. In other words, even when the cam ring 8 is deformed due to the pump inner pressure, the cam profile includes the deviation region radially outwardly deviating from the perfect-circle cam profile in the discharge region.

Next, the shape of the distal end of each of the vanes 16 will be described.

FIG. 6 illustrates the shape of the distal end of the vane 16. The vane 16 includes a vane distal end curved surface portion 16 a. The vane distal end curved surface portion 16 a has a circular-arc shape convexed radially outwardly in cross section perpendicular to the rotational axis O.

Now, assuming that rv represents the curvature radius (a curvature center p6) of the vane distal end curved surface portion 16 a, and T represents the thickness (the plate thickness) of the vane 16 in the circumferential direction regarding the rotational axis O, the vane 16 has a shape that satisfies 2×T≤rv.

FIG. 7 illustrates a contact range between the vane distal end curved surface portion 16 a and the inner peripheral edge 8 a of the cam ring 8. A fourth axis L4 is defined to refer to an axis perpendicular to the rotational axis O and passing through the center of the vane 16 in the circumferential direction in cross section perpendicular to the rotational axis O. Further, a fifth axis L5 is defined to refer to a line segment connecting a contact point p7 between the vane distal end curved surface portion 16 a and the inner peripheral edge 8 a of the cam ring 8 and the curvature center p6. Then, a contact angle δ is defined to refer to a minor angle of angles formed between the fourth axis L4 and the fifth axis L5. In the intake region, the contact angle δ changes according to the phase (the pump rotational angle), and the vane 16 is in contact with the inner peripheral edge 8 a of the cam ring 8 in a range exceeding 40% (for example, 60%) of the length of the outer peripheral edge of the vane distal end curved surface portion 16 a.

Next, functions and effects of the first embodiment will be described.

The cam profile of the cam ring 8 according to the first embodiment includes the deviation region radially outwardly deviating from the perfect-circle cam profile in the intake region. In other words, the cam profile in the intake region is shaped as a non-perfect circle (an ellipse). This configuration causes a change in the range where the vane distal end curved surface portion 16 a slidably moves on the inner peripheral edge 8 a of the cam ring 8 according to the phase in the intake region, thereby reducing the local wear of the vane 16. As illustrated in FIG. 8, in the intake region, the contact position between the vane distal end curved surface portion 16 a and the inner peripheral edge 8 a of the cam ring 8 largely changes according to the pump rotational angle. The reduction in the local wear of the vane 16 leads to a reduction in heat generation accompanying this wear. This makes it unlikely to run out of the oil film due to the reduction in the viscosity of the hydraulic oil interposed between the vane distal end curved surface portion 16 a and the inner peripheral edge 8 a. Therefore, the present configuration can reduce galling and seizure accompanying the contact between the metallic materials. As a result, the present configuration can improve the durability of the vane 16 and the cam ring 8. Further, the present configuration eliminates the necessity of applying coating (surface processing) for preventing the seizure on the distal end of the vane 16, thereby being able to achieve a considerable cost reduction.

On the cam ring 8, the first cam profile deviation amount Δr1 is smaller than the second cam profile deviation amount Δr2. In other words, even when the cam ring 8 is deformed due to the pump inner pressure, the cam profile includes the deviation region radially outwardly deviating from the perfect-circle cam profile in the discharge region. As a result, the present configuration can maintain the effect of reducing the galling and the seizure of the vane 16 even when the cam ring 8 is deformed due to the pump inner pressure.

The deviation region deviates from the perfect-circle cam profile outwardly in the radial direction regarding the rotational axis. Now, suppose that the cam profile radially inwardly deviates from the perfect-circle cam profile in the intake region as a comparative example of the first embodiment. As illustrated in FIG. 9, this comparative example maintains the compression state in most of the intake region and reduces the section where the hydraulic oil can be sucked, thereby raising a possibility that a trouble such as cavitation occurs due to the shortage of the intake amount. On the other hand, the first embodiment radially outwardly deviates the cam profile from the perfect-circle cam profile, thereby allowing the hydraulic oil to be sucked throughout the entire intake region and ensuring the acquisition of the sufficient intake amount, thus being able to reduce the occurrence of a trouble such as cavitation. Further, the cam profile radius change rate should be changed smoothly from a positive value to a negative value with the aim of preventing abnormal noise in the section between the termination end 21 b of the second intake port 21 and the start end 23 a of the first discharge port 23 (i.e., a second confinement region). Therefore, in the case where the cam profile radially inwardly deviates from the perfect-circle cam profile like the comparative example, the cam profile radius change rate should be sharply changed immediately before the second confinement region, and this leads to the complication of the cam profile. On the other hand, in the case where the cam profile radially outwardly deviates from the perfect-circle cam profile like the first embodiment, the intake region and the second confinement region can be smoothly connected, and this can prevent the complication of the cam profile.

The deviation region is provided throughout the entire intake region. Due to this configuration, the variable displacement vane pump 1 can sufficiently secure the section (the circumferential range of the cam ring 8) in which the sliding range of the vane distal end curved surface portion 16 a is changed.

The cam profile of the cam ring 8 includes the deviation region even at the time of the minimum eccentricity. At the time of the minimum eccentricity, the distance between the rotational axis O and the center P is minimized, and therefore the cam profile tends to relatively less change and the vane distal end curved surface portion 16 a tends to slidably move in a narrower range. For example, at the time of the relief when the relief valve 33 is opened, the vane distal end curved surface portion 16 a is pressed by a strong force and the eccentricity amount of the cam ring 8 reduces, which facilitates the occurrence of the galling and the seizure of the vane distal end curved surface portion 16 a. Therefore, the galling and the seizure of the vane 16 at the time of the minimum eccentricity can be reduced by setting the cam profile so as to include the deviation region at the time of the minimum eccentricity.

The vane 16 includes the circular arc-shaped vane distal end curved surface portion 16 a at the distal end thereof on the radially outer side, and the outer peripheral edge of the vane distal end curved surface portion 16 a is in contact with the inner peripheral edge 8 a of the cam ring 8 in the range accounting for more than 40% thereof in the intake region. This configuration makes usable a wide range of the distal end portion of the vane 16, thereby being able to effectively reduce the local wear.

Assuming that rv represents the curvature radius of the vane distal end curved surface portion 16 a and T represents the thickness of the vane 16, the vane 16 satisfies 2×T≤rv. As illustrated in FIG. 10, the contact region of the vane 16 can be considerably expanded compared to the conventional perfect-circle cam profile even when only the cam profile of the cam ring 8 according to the first embodiment is employed. By further increasing the curvature radius rv of the vane distal end curved surface portion 16 a to more than twice the plate thickness T of the vane 16, the present configuration can further expand the contact range of the vane 16 to more than twice, thereby being able to further effectively reduce the local wear of the vane 16.

Second Embodiment

A second embodiment has a basic configuration similar to the first embodiment, and therefore will be described focusing only on differences from the first embodiment.

FIG. 11 illustrates the relationship between the rotational axis O of the driving shaft 6 and the center P of the inner peripheral edge 8 a of the camp ring 8 in the variable displacement vane pump 1 according to the second embodiment.

The second embodiment is different from the first embodiment in terms of the fact that the center P of the cam profile of the cam ring 8 is disposed offset to the intake region side. The cam ring 8 is provided in the pump element containing space 4 a so as to constantly deviate from the rotational axis O toward the intake region side regardless of whether the variable displacement vane pump 1 is in operation or out of operation and the eccentricity amount of the cam ring 8 with respect to the rotor 7.

The second embodiment can shift the cam profile radius change rate in the intake region further to the positive side by positioning the cam ring 8 offset to the intake region side, i.e., placing the cam ring 8 in a so-called eccentric lift state. In other words, due to the eccentric lift, the present configuration causes the cam profile to further radially outwardly deviate from the perfect-circle cam profile, and therefore can further expand the deviation region at the time of the minimum eccentricity and the deformation of the cam ring. As a result, this configuration can reduce the galling and the seizure of the vane 16 at the time of the minimum eccentricity and the deformation of the cam ring.

Other Embodiments

Having described the embodiments for implementing the present invention, the specific configuration of the present invention is not limited to the configurations of the embodiments, and the present invention also includes even a design modification and the like thereof made within a range that does not depart from the spirit of the present invention, if any.

The center of the outer peripheral surface of the cam ring may be deviated from the center of the inner peripheral surface of the cam ring.

The pressure plate and/or the adapter ring may be provided integrally with the front housing.

The intake port and the discharge port may be provided on only one of the pressure plate and the rear housing.

The vane distal end curved surface portion may contact the cam ring in a different manner as long as contacting the inner peripheral edge of the cam ring in the range exceeding 40% of the length of the outer peripheral edge thereof.

In the following description, technical ideas recognizable from the above-described embodiments will be described.

A pump apparatus, according to one configuration thereof, includes a pump housing. The pump housing includes a pump element containing space, an intake passage, a discharge passage, an intake port, and a discharge port. The intake passage is connected to the intake port. The discharge passage is connected to the discharge port. The pump apparatus further includes a driving shaft rotatably provided in the pump housing, a rotor provided on the driving shaft and including a plurality of slits, a plurality of vanes provided movably in the plurality of slits, respectively, and made from a metallic material, and a cam ring. The cam ring is annularly formed, and is provided in the pump element containing space. The cam ring forms a plurality of pump chambers together with the rotor and the plurality of vanes, and a first fluid pressure chamber and a second fluid pressure chamber are formed in the pump element containing space. The intake port is opened to a region where a volume of the pump chamber increases according to a rotation of the rotational shaft among the plurality of pump chambers. The discharge port is opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers. In a space formed on a radially outer side of the cam ring in a radial direction regarding a rotational axis of the driving shaft, the first fluid pressure chamber is provided in a portion in this space where the volume reduces as an eccentricity amount between the rotational axis of the driving shaft and a center of an inner peripheral edge of the cam ring increases. In the space formed on the radially outer side of the cam ring in the radial direction regarding the rotational axis of the driving shaft, the second fluid pressure chamber is provided in a portion in this space where the volume increases as the eccentricity amount between the rotational axis of the driving shaft and the center of the inner peripheral edge of the cam ring increases. The cam ring is movable in the pump element containing space based on a pressure difference between the first fluid pressure chamber and the second fluid pressure chamber. Assuming that a cam profile refers to a line extending along the inner peripheral edge of the cam ring, an intake region corresponds to a range from a start end to a termination end of the intake port in a circumferential direction regarding the rotational axis of the driving shaft, a first axis refers to an axis extending perpendicularly to the rotational axis of the driving shaft and passing through a point that divides in half a section between a termination end of the discharge port and the start end of the intake port in the circumferential direction regarding the rotational axis of the rotational shaft in cross section perpendicular to the rotational axis of the driving shaft, a second axis refers to an axis extending perpendicularly to the first axis and passing through a point that divides in half a section between a pair of intersection points at which the cam profile and the first axis intersect with each other, a cam profile central point refers to an intersection point between the first axis and the second axis, a third axis refers to an axis passing through the cam profile central point and the termination end of the intake port, a perfect-circle cam profile radius refers to a length between a point at which the third axis and the cam profile intersect with each other and the cam profile central point, and a perfect-circle cam profile refers to a circular arc centered at the cam profile central point and having the perfect-circle cam profile radius, the cam profile includes a deviation region deviating from the perfect-circle cam profile outwardly or inwardly in the radial direction regarding the rotational axis of the driving shaft in the intake region.

According to a further preferable configuration, in the above-described configuration, assuming that the cam profile in a first state refers to the cam profile when the driving shaft is stopped and a discharge pressure is not applied to the discharge region and the cam profile radius in the first state refers to a distance from the cam profile central point to the cam profile in the first state, the cam profile in a second state refers to the cam profile when the discharge pressure is applied to the discharge region according to the rotation of the driving shaft and the cam profile radius in the second state refers to a distance from the cam profile central point to the cam profile in the second state, a first cam profile deviation amount refers to a maximum value of an absolute value of a difference between the cam profile radius in the first state and the cam profile radius in the second state when comparing the cam profile in the first state and the cam profile in the second state at the same position in the circumferential direction regarding the rotational axis of the driving shaft in the intake region, and a second cam profile deviation amount refers to a maximum value of an absolute value of a difference between the perfect-circle cam profile radius and the cam profile radius in the first state when comparing the perfect-circle cam profile and the cam profile in the first state at the same position in the circumferential direction regarding the rotational axis of the driving shaft in the intake region, the cam ring has such a shape that the cam profile in the first state satisfies the first cam profile deviation amount<the second cam profile deviation amount.

According to another preferable configuration, in any of the above-described configurations, the deviation region deviates from the perfect-circle cam profile outwardly in the radial direction regarding the rotational axis of the driving shaft.

According to further another preferable configuration, in any of the above-described configurations, the deviation region is provided throughout the entire intake region.

According to further another preferable configuration, in any of the above-described configurations, the cam profile of the cam ring includes the deviation region when the eccentricity amount between the rotational axis of the driving shaft and the center of the inner peripheral edge of the cam ring is minimized.

According to further another preferable configuration, in any of the above-described configurations, each of the vanes includes a vane distal end curved surface portion provided at a distal end thereof on an outer side in the radial direction regarding the rotational axis of the driving shaft. The vane distal end curved surface portion has a circular-arc shape convexed radially outwardly in cross section perpendicular to the rotational axis of the driving shaft. The vane is in contact with the inner peripheral edge of the cam ring in a range exceeding 40% of a length of an outer peripheral edge of the vane distal end curved surface portion in the intake region.

According to further another preferable configuration, in any of the above-described configurations, each of the vanes includes a vane distal end curved surface portion provided at a distal end thereof on an outer side in the radial direction regarding the rotational axis of the driving shaft. The vane distal end curved surface portion has a circular-arc shape convexed radially outwardly and having a curvature radius rv in cross section perpendicular to the rotational axis of the driving shaft. Assuming that T represents a thickness of the vane in the circumferential direction regarding the rotational axis of the driving shaft, the vane has a shape that satisfies 2×T≤rv.

According to further another preferable configuration, in any of the above-described configurations, assuming that the cam profile in a first state refers to the cam profile when the driving shaft is stopped and a discharge pressure is not applied to the discharge region, and the cam profile in a second state refers to the cam profile when the discharge pressure is applied to the discharge region according to the rotation of the driving shaft, the cam ring is provided in the pump element containing space in such a manner that a center of the cam profile in the first state and a center of the camp profile in the second state deviate from the first axis toward the intake region side.

The present invention shall not be limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail to facilitate a better understanding of the present invention, and the present invention shall not necessarily be limited to the configuration including all of the described features. Further, a part of the configuration of some embodiment can be replaced with the configuration of another embodiment. Further, some embodiment can also be implemented with a configuration of another embodiment added to the configuration of this embodiment. Further, each of the embodiments can also be implemented with another configuration added, deleted, or replaced with respect to a part of the configuration of this embodiment.

The present application claims priority under the Paris Convention to Japanese Patent Application No. 2018-167511 filed on Sep. 7, 2018. The entire disclosure of Japanese Patent Application No. 2018-167511 filed on Sep. 7, 2018 including the specification, the claims, the drawings, and the abstract is incorporated herein by reference in its entirety.

REFERENCE SIGNS LIST

-   -   1 variable displacement vane pump (pump apparatus)     -   4 pump housing     -   4 a pump element containing space     -   5 pump element     -   6 driving shaft     -   7 rotor     -   7 a slit     -   8 cam ring     -   8 a inner peripheral edge     -   14 a first fluid pressure chamber     -   14 b second fluid pressure chamber     -   16 vane     -   16 a vane distal end curved surface portion     -   17 pump chamber     -   18 first intake port     -   19 a intake passage     -   19 b discharge passage     -   21 second intake port     -   21 b termination end     -   23 first discharge port     -   23 a start end     -   25 second discharge port     -   O rotational axis     -   P center 

1. A pump apparatus comprising: a pump housing, the pump housing including a pump element containing space, an intake passage, a discharge passage, an intake port, and a discharge port, the intake passage being connected to the intake port, the discharge passage being connected to the discharge port, the pump apparatus further comprising: a driving shaft rotatably provided in the pump housing; a rotor provided on the driving shaft and including a plurality of slits; a plurality of vanes provided movably in the plurality of slits, respectively, the plurality of vanes being made from a metallic material; and a cam ring, wherein the cam ring is annularly formed, and is provided in the pump element containing space, wherein the cam ring forms a plurality of pump chambers together with the rotor and the plurality of vanes, and a first fluid pressure chamber and a second fluid pressure chamber are formed in the pump element containing space, wherein the intake port is opened to a region where a volume of the pump chamber increases according to a rotation of the rotational shaft among the plurality of pump chambers, wherein the discharge port is opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers, wherein, in a space formed on a radially outer side of the cam ring in a radial direction regarding a rotational axis of the driving shaft, the first fluid pressure chamber is provided in a portion in this space where the volume reduces as an eccentricity amount between the rotational axis of the driving shaft and a center of an inner peripheral edge of the cam ring increases, wherein, in the space formed on the radially outer side of the cam ring in the radial direction regarding the rotational axis of the driving shaft, the second fluid pressure chamber is provided in a portion in this space where the volume increases as the eccentricity amount between the rotational axis of the driving shaft and the center of the inner peripheral edge of the cam ring increases, wherein the cam ring is movable in the pump element containing space based on a pressure difference between the first fluid pressure chamber and the second fluid pressure chamber, and wherein, assuming that a cam profile refers to a line extending along the inner peripheral edge of the cam ring, an intake region corresponds to a range from a start end to a termination end of the intake port in a circumferential direction regarding the rotational axis of the driving shaft, a first axis refers to an axis extending perpendicularly to the rotational axis of the driving shaft and passing through a point that divides in half a section between a termination end of the discharge port and the start end of the intake port in the circumferential direction regarding the rotational axis of the rotational shaft in cross section perpendicular to the rotational axis of the driving shaft, a second axis refers to an axis extending perpendicularly to the first axis and passing through a point that divides in half a section between a pair of intersection points at which the cam profile and the first axis intersect with each other, a cam profile central point refers to an intersection point between the first axis and the second axis, a third axis refers to an axis passing through the cam profile central point and the termination end of the intake port, a perfect-circle cam profile radius refers to a length between a point at which the third axis and the cam profile intersect with each other and the cam profile central point, and a perfect-circle cam profile refers to a circular arc centered at the cam profile central point and having the perfect-circle cam profile radius, the cam profile includes a deviation region deviating from the perfect-circle cam profile outwardly or inwardly in the radial direction regarding the rotational axis of the driving shaft in the intake region.
 2. The pump apparatus according to claim 1, wherein, assuming that the cam profile in a first state refers to the cam profile when the driving shaft is stopped and a discharge pressure is not applied to the discharge region, and the cam profile radius in the first state refers to a distance from the cam profile central point to the cam profile in the first state, the cam profile in a second state refers to the cam profile when the discharge pressure is applied to the discharge region according to the rotation of the driving shaft, and the cam profile radius in the second state refers to a distance from the cam profile central point to the cam profile in the second state, a first cam profile deviation amount refers to a maximum value of an absolute value of a difference between the cam profile radius in the first state and the cam profile radius in the second state when comparing the cam profile in the first state and the cam profile in the second state at the same position in the circumferential direction regarding the rotational axis of the driving shaft in the intake region, and a second cam profile deviation amount refers to a maximum value of an absolute value of a difference between the perfect-circle cam profile radius and the cam profile radius in the first state when comparing the perfect-circle cam profile and the cam profile in the first state at the same position in the circumferential direction regarding the rotational axis of the driving shaft in the intake region, the cam ring has such a shape that the cam profile in the first state satisfies the first cam profile deviation amount<the second cam profile deviation amount.
 3. The pump apparatus according to claim 1, wherein the deviation region deviates from the perfect-circle cam profile outwardly in the radial direction regarding the rotational axis of the driving shaft.
 4. The pump apparatus according to claim 1, wherein the deviation region is provided throughout the entire intake region.
 5. The pump apparatus according to claim 1, wherein the cam profile of the cam ring includes the deviation region when the eccentricity amount between the rotational axis of the driving shaft and the center of the inner peripheral edge of the cam ring is minimized.
 6. The pump apparatus according to claim 1, wherein each of the vanes includes a vane distal end curved surface portion provided at a distal end thereof on an outer side in the radial direction regarding the rotational axis of the driving shaft, wherein the vane distal end curved surface portion has a circular-arc shape convexed radially outwardly in cross section perpendicular to the rotational axis of the driving shaft, and wherein the vane is in contact with the inner peripheral edge of the cam ring in a range exceeding 40% of a length of an outer peripheral edge of the vane distal end curved surface portion in the intake region.
 7. The pump apparatus according to claim 1, wherein each of the vanes includes a vane distal end curved surface portion provided at a distal end thereof on an outer side in the radial direction regarding the rotational axis of the driving shaft, wherein the vane distal end curved surface portion has a circular-arc shape convexed radially outwardly and having a curvature radius rv in cross section perpendicular to the rotational axis of the driving shaft, and wherein, assuming that T represents a thickness of the vane in the circumferential direction regarding the rotational axis of the driving shaft, the vane has a shape that satisfies 2×T<rv.
 8. The pump apparatus according to claim 1, wherein, assuming that the cam profile in a first state refers to the cam profile when the driving shaft is stopped and a discharge pressure is not applied to the discharge region, and the cam profile in a second state refers to the cam profile when the discharge pressure is applied to the discharge region according to the rotation of the driving shaft, the cam ring is provided in the pump element containing space in such a manner that a center of the cam profile in the first state and a center of the camp profile in the second state deviate from the first axis toward the intake region side. 